Unfallbericht:JA8119 was a Japan Air Lines Boeing 747SR, a short range variant of the Boeing 747 Series 100. The was aircraft specifically configured for domestic flights with a high density seating arrangement. On June 2, 1978 the aircraft operated on a flight to Osaka (ITM). It floated after touchdown and on the second touchdown the tail struck the runway. The aircraft sustained substantial damage to the rear underside of the fuselage. The rear pressure bulkhead was cracked as well. The aircraft was repaired by Boeing. Engineers replaced the lower part of the rear fuselage and a portion of the lower half of the bulkhead.Seven years later, on August 12, 1985, JA8119 had completed four domestic flights when it landed at Tokyo-Haneda (HND) at 17:17. The next flight was to be flight 123 to Osaka (ITM). The aircraft took off from Tokyo-Haneda at 18:12. Twelve minutes later, while climbing through 23900 feet at a speed of 300 knots, an unusual vibration occurred. An impact force raised the nose of the aircraft and control problems were experienced. A decompression had occurred and the crew got indications of problems with the R5 door. In fact, the rear pressure bulkhead had ruptured, causing serious damage to the rear of the plane. A portion of its vertical fin, measuring 5 m together with the section of the tailcone containing the auxiliary power unit (APU) were ripped off the plane. Due to the damage, the hydraulic pressure dropped and ailerons, elevators and yaw damper became inoperative. Controlling the plane was very difficult as the airplane experienced dutch rolls and phugoid oscillations (unusual movement in which altitude and speed change significantly in a 20-100 seconds cycle without change of angle of attack).The aircraft started to descend to 6600 feet while the crew tried to control the aircraft by using engine thrust. Upon reaching 6600 feet the airspeed had dropped to 108 knots. The aircraft then climbed with a 39 degree pitch-up to a maximum of approx. 13400 feet and started to descend again. At 18:56 JAL123 finally brushed against a tree covered ridge, continued and struck the Osutaka Ridge, bursting into flames.

CAUSE: "It is estimated that this accident was caused by deterioration of flying quality and loss of primary flight control functions due to rupture of the aft pressure bulkhead of the aircraft, and the subsequent ruptures of a part of the fuselage tail, vertical fin and hydraulical flight control systems.The reason why the aft pressure bulkhead was ruptured in flight is estimated to be that the strength of the said bulkhead was reduced due to fatigue cracks propagating at the spliced portion of the bulkhead's webs to the extent that it became unable to endure the cabin pressure in flight at that time.The initiation and propagation of the fatigue cracks are attributable to the improper repairs of the said bulkhead conducted in 1978, and it is estimated that the fatigue cracks having not be found in the later maintenance inspection is contributive to their propagation leading to the rupture of the said bulkhead."

Within 30 days after the effective date of this AD, perform a one-time visual inspection of the aft side of the aft pressure bulkhead for evidence of repairs or damage.

Issued: 05-DEC-1985

To: FAA

A-85-133

Require the manufacturer to modify the design of the Boeing 747 empennage so that in the event that a significant pressure buildup occurs in the normally unpressurized empennage, the structural integrity of the stabilizers and their respective control surfaces will be protected against catastrophic failure, and to incorporate associated modifications on all Boeing 747 airplanes. (Closed - Acceptable Action)

Issued: 05-DEC-1985

To: FAA

A-85-134

Require the manufacturer to modify the design of the Boeing 747 hydraulic systems so that in the event a significant pressure buildup occurs in the normally unpressurized empennage, the integrity of all four hydraulic systems will not be impaired, and to incorporate associated modifications on all Boeing 747 airplanes. (Closed - Acceptable Action)

Issued: 05-DEC-1985

To: FAA

A-85-135

Reevaluate the design of the Boeing 747 and 767 aft pressure bulkhead by requiring Boeing to analyze and test further the bulkhead to demonstrate the validity of the fail-safe "flapping" failure mode. (Superseded by A-85-138) (Closed - Superseded)

Issued: 05-DEC-1985

To: FAA

A-85-136

Evaluate any procedures approved to repair B-747 and B-767 aft pressure bulkhead to assure that the repairs do not affect the "fail-safe" concept of the bulkhead design which is intended to limit the area of pressure relief in the event of a structural failure. (Closed - Acceptable Action)

Issued: 05-DEC-1985

To: FAA

A-85-137

Revise the inspection program for the B-747 rear pressure bulkhead, to establish an inspection interval wherein inspections beyond the routine visual inspection would be performed to detect the extent of possible multiple site fatigue cracking. (Closed - Acceptable Action)

Issued: 13-DEC-1985

To: FAA

A-85-138

Determine which transport category airplanes have dome-shaped aft pressure bulkheads and ascertain that the "fail-safe" criteria for the pressure bulkheads of those airplanes have been satisfactorily evaluated.

Issued: 13-DEC-1985

To: FAA

A-85-139

Evaluate any procedures approved to repair the aft pressure bulkhead of any airplanes which incorporate a dome-type of design to assure that the effected repair does not derogate the fail-safe concept of the bulkhead.

Issued: 13-DEC-1985

To: FAA

A-85-140

Issue a maintenance alert bulletin to persons responsible for the engineering approval of repairs to emphasize that the approval adequately consider the possibility of influence on ultimate failure modes or other fail-safe design criteria.

Issued: 19-MAY-1986

To: Boeing 747

AD 86-08-02

Requiring the addition of a structural cover for the opening within the empennage to provide access to the vertical fin of all B747 models. This is to prevent structural failure of the vertical fin in the event of failure of the aft pressure bulkhead.

Issued: 13-JUL-1987

To: Boeing 747

AD 87-12-04

Requiring installation of a hydraulic fuse in the number 4 hydraulic system on Boeing Model 747 series airplanes.

Issued: 10-DEC-1987

To: Boeing 747

AD 87-23-10

Requiring inspection for damage and cracking of the aft pressure bulkhead on Boeing Model 747 airplanes. (Superseded by AD 98-20-20)

Superseded AD 98-20-20, requiring that a one-time inspection to detect cracking of the upper segment of the bulkhead web be accomplished repetitively, and adds additional repetitive inspections to detect cracking of the upper and lower segments of the aft bulkhead web.

This map shows the airport of departure and the intended destination of the flight. The line between the airports does not display the exact flight path. Distance from Tokyo-Haneda Airport to Osaka-Itami Airport as the crow flies is 401 km (251 miles).

This information is not presented as the Flight Safety Foundation or the Aviation Safety Network’s opinion as to the cause of the accident. It is preliminary and is based on the facts as they are known at this time.